You seem like a real self-starter, and the other work you've done is probably helping you now. Again, great job with everything. My comments aren't really criticisms, but rather suggestions for taking the next step.
My general response is that the playing sounds inexperienced (understandably), although you are playing very sophisticated music and, in some ways, playing it quite well. It has a lovely clarity, but the effort of playing correctly is perceptible and it makes the playing sound young and too careful. I wouldn't even bring this up to anybody else, since this quality matures on its own over time, but I respect that you are very invested in your playing and serious about learning quickly. Since you know your way around some of the variations so well, I think it’s a natural time to start experimenting with sound. And I believe the way to experiment with sound is to first experiment with feeling, because our physical feeling and ease for the instrument is reflected in our sound.
I have a harmless hobby of taking up new instruments, and generally can get to a decent level of playing in a very short time. I use an exercise or game that I think of as “pretended fluency.” First, I sit down with the instrument and imagine I’m an expert at it. I think, how would it feel to know how to do this deep in my bones, to have done it since I was born? I imitate the postures and movements of people who are incredibly fluent and comfortable on the same instrument, but even more than that, I imitate MYSELF as I imagine I would feel if I were utterly fluent. Then I improvise—not improvising a piece of music, but improvising how to play the instrument. I choose some general character of music: regal, lyrical, playful, stormy etc., then play nonsense in that character, and do it with authority. Musically, it’s gibberish, but it's about discovering the feel of playing fluently, not composing a piece or having it make sense. What I'm doing here is similar to “catching” the accent of a foreign language--I'm trying to catch the flavor of the instrument, and I can't stress this enough: how it feels, not how it sounds. The next thing I do is to play an easy piece, but play it as if I’m able to play ANYTHING on this instrument, I’m just choosing to play something easy. That's it. To re-cap: 1. Sit and move fluently, imagine feeling completely at home on this instrument. 2. Pretend-play some idea or feeling with conviction. 3. Play a real piece that's very simple, but play it as an expert totally at ease.
This works, and I think the reason it works is that it’s how we learn language. We don’t learn words and grammar first; we learn them last (we start developing the idea of and capacity for grammar as babies, but it's one of the last steps we actually use). The early talking of a toddler is strings of nonsense syllables with all the inflections and character of mature conversation. They imitate the feeling and the idea of speaking long before they actually speak. Conversely, when we learn a new language as adults, we learn words, grammar and devices/idioms first, and we carefully proceed, trying to speak as correctly as possible. But then that’s how we sound, like we’re trying to speak as correctly as possible. That’s what I hear in your playing right now, the correctness and caution. But since you have so many technical things sorted out at this point, I think it would be worthwhile to forget about all that in some of your practicing, just play your fanny off, and see what happens.
Best to you!
Topic: An attempt at the Goldberg Variations, progression of learning